Electrode with molded insulation



y 1951 H. M. RICHARDSON ELECTRODE WITH MOLDED INSULATION Filed March 5, 1946 GLASS BONDED POWERED M/GA GLASS BONDED POWDERE D M/CA I N V EN TOR. f/f/vk'y M flay/1:050 BY JWoPMs-m' Patented July 3, 1951 ELECTRODE wrrrr MOLDED INSULATION Henry M. Richardson, Springfield, Mass., assignor to Mycalex Corporation of America, Clifton, N. J a corporation or New Jersey Application March 5, 1946, Serial No. 652,154 2 Claims. (01. 174-152) The present invention is directed to structures of electrodes, particularly electrodes intended for high frequency, high voltage applications and embodyin molded insulation and metallic conducting elements.

The structure of the present invention is related to that described in the application of Albert J. Monack, Serial No. 582,397, filed March 12, 1945, now abandoned, entitled "Electrode Structures. In said application there have been described various forms of electrodes embodying generally one or more electrodes for conducting current, surrounded by a special insulating composition and held in a metal sleeve or the like. The composition used may be termed a glass bonded mica, wherein a uniform mixture of finely divided mica and a special glass also in finely divided form are molded under heat and pressure to form a unitary electrode structure.

' Electrode structures of this type have been found quite useful in the art, particularly in radio transformers, crystal holders and other applications where a hermetic seal of the lead-in connection is important. While these structures operated quite well under the circumstances, it often becomes desirable to provide an electrode of high electrical conductivity Where it i necessary or desirable to carry relatively high currents. In such cases the structure of such application might not be fully effective in that a hermetic seal between the high conductivity electrode and the molded insulating composl-q tion might not in all cases be obtained. Also, difiiculty is sometimes encountered where a relatively large number of electrodes are held in a single body of insulating material or where said body is relatively large. The metal eyelet or ring-like outer member may, because of the large amount of expansion and contraction of large masses and bodies, during and after the molding operation, result in some cases in the seal not being perfect.

The present invention is designed to overcome such difliculties and disadvantage noted above and to provide an electrode structure wherein relatively large bodies of insulating compositions may be incorporated and a hermetic seal be obtained.

It is also amon the objects of the present invention to provide a structure wherein the electrode itself shall be of a metal having a high degree of electrical conductivity and usually a high coeflicient of expansion, but which nevertheles is hermetically sealed to the body of insulating material which has a lower coeflicient of expansion.

It is further among the objects of the present invention to provide an electrode structure of the type described, having an outer eyelet or ring surrounding the insulatin material and attached thereto, wherein the structure is such as to provide a hermetic seal even under conditions of large expansion and contraction.

In practicing the present invention, there is provided an electrode of any desired form. On the electrode is secured in an integral manner, either by forming or by welding or the like, a cup-shaped member. Said member may be of the same or of different material than the electrode. The sides of the cup embrace the mold ing composition and after the molding operation is complete and the assembly cooled the shrinkage of the cup, slightly greater than that of the insulating material, causes the sides thereof to firmly grip said insulating material and provide an hermetic seal.

The eyelet structure may consist of a band or ring-like member surrounding the molded insulating and firmly gripping the same by reason of the shrinkage of the metal upon cooling after the molding operation. The eyelet may have a pair of flanges projecting into the body of insulating material and producin an additional force of compression upon that part-0f the insulating which lies intermediate said inwardly projecting parts. This insures that under all conditions, even when large masses of molding material and metal are incorporated in the structure and the heatin and cooling is over wide temperature ranges, the seal of the eyelet to the insulating material will not be disturbed.

In the accompanyin drawing, in which like reference characters indicate like parts,

Fig. 1 is a top plan view of a multiple electrode structure made in accordance with the present invention;

Fig. 2 is a vertical cross-sectional view taken through two of the electrodes of Fig. 1;

Fig. 3 is a vertical cross-sectional view of an eyelet or rin for incorporation into an electrode structure, said ring being a modified form of that shown in Fig. 2;

Fig. 4 is a vertical cross-sectional view of another form of structure made in accordance with the present invention, wherein flanges are formed on the electrode itself;

Fig. 5 is a vertical cross-sectional view of a further modified form of eyelet used in the present structure, and

Fig. 6 is a further modification of an electrode structure formed in accordance with the present invention.

In the embodiment shown in Figs. 1 and 2, there are provided a plurality of electrodes I made of copper, aluminum or the like, and having a high electrical conductivity, they being shown as rods, although any suitable form may be provided. A cup 2 having an opening in the bottom is mounted over electrode I and is hermetically secured thereto by brazing 3. Preferably the cup is of a material with slightly higher coefficient of expansion than the insulating material. The sides 4 of the cup depend from the bottom, with said. sides being substantially parallel to the electrode. A ring or eyelet having a band portion 6 surrounds the series of electrodes, and inwardly projecting flanges I and y 8 are provided integrally with band 6. Ring 5 is adapted to be suitably secured in a piece of electrical equipment. A body of molded insulating material 9 surrounds electrodes I and is contained within eyelet 5, some of the material I0 entering cups 2 and some of the material II entering into the space between flanges I and 8. Extensions I2 of insulating material integral with body 9 surround the electrodes to provide additional insulating value.

The substance of which the molded insulating material 9 is made is similar to that described in the aforesaid pending application, namely a glass bonded mica. Usually the glass or frit contained in the composition consists or comprises essentially of lead borate or a mixture of borates of lead, alkali metals and alkali earth metals. It may contain other constituents such as a flux, of which cryolite is an example. The frit in finely divided form is mixed with mica, also in finely divided form, the proportions being usually about 40 to 50% of mica and 60 to 50% of irit. The homogeneous mixture constitutes a composition which may be molded at high temperatures. The temperature of the material at the time of molding may be as high as 1200 to 1300 F. or even higher.

In order to produce the structures shown in Figs. 1 and 2, the electrodes I are plac:d in a suitable mold, the eyelet 5 is placed in position, the mold is maintained at a relatively high temperature and the molding composition as described above at a, molding temperature is introduced into the mold preferably by injection at a suflicient pressure so as to fill the mold con".- pletely. The mold is then opened the electrode structure removed therefrom and allowed to cool.- If desired, it may be cooled in a suitable annealing oven so as to retard temperature changes and to avoid strains due to rapid cooling.

The electrodes and. cups having a high coefl cient of expansion, somewhat higher than that of the glass bonded mica, will in cooling to room temperature contract a substantial amount, causing the sides 4 of the cups 2 to firmly grip the insulating material. Even though the electrodes themselves may have a tendency to contract away from insulation 8, t1 2 ripping of sides 4 of the cups will insure a hermetic seal. The eyelets, if they are made of material having a higher coeficient of expansion than the insulation, will have the band 6 shrunk or contracted upon the insulation 9 and thus form a hermetic seal. At the same time, because of the lateral shrinkage of band 6, flanges I and 8 will tend to approach each other and exert pressure upon insulation II and further insure a hermetic seal at such areas.

According to the modification shown in Figure 3 the eyelet may be made in two parts, a disc-like part I6 and a member I1 having a disclike portion I5, a band I3 and an inwardly extending flange I4. The disc-like portion I5 is attached to the disc member I6 in any suitable way.

In Fig. 5 there is shown an eyelet structure quite similar to that shown in Fig. 2 but of somewhat different character in that instead of being a fabricated element, it may be machined or cut or otherwise formed from a single piece. It is adaptable for production cheaply in large quantities in the well-known automatic screw machines.

In Fig. 4, the electrode l8 has formed thereon a pair of lateral extensions or flanges I9 and 20 spaced a substantial distance apart. As shown, said flanges are provided on a separate metal member 2| which is welded, brazed or otherwise made integral with electrode I8. It may be either of the same metal or a different metal than said electrode. Such structure replaces the cup shown in Fig. 2 and has a similar effect in the compression of the insulating material 9. After the molding operation is com plete, the cooling of the article down to room temperature causes contraction of electrode I8 and a tendency for flanges I9 and 20 to approach each other. This puts added compression upon the insulating material contained therebetween and gives a hermetic seal. An eyelet 22 having a band 23 may be provided, the latter being of a metal having a higher coefficient of expansion than the insulating material, and gripping the same by contraction.

The form of the invention shown in Fig. 6 is somewhat difierent than the other modification in that instead of providing a solid body of insulating material, there is a hollow body and the electrode is not in contact with the insulation. The electrode 24 has a cup 25 secured thereto at 26 by brazing or the like. The sides 21 of the cup are substantially parallel to electrode 24. Insulating material 28 is molded within the cup in such a manner as to leave an open space 29 around the electrode. Sleeve 30, having a band 3I, surrounds the insulation 28 and is shrunk thereon as is described above. This form of the invention allows a limited amount of movement of the electrode relative to the insulating material which is of advantage in certain electrical apparatus.

Although I have described my invention setting forth several embodiments thereof, it will be .quite apparent that various modifications in the invention may be made without departing from the spirit thereof. For instance, the insulating compositions may be varied in various ways as for instance, by incorporation of added materials such as titanium dioxide to adjust the electrical properties thereof. In place of allor a part of the powdered mica, which represents the lamellar type of insulating material, a fibrillar type of insulating material, such as asbestos (which is preferably powdered) may be substituted. The form of the cups and eyelets and flanges may be anything desired and-they need not necessarily be symmetrical in form. Other metals than those herein stated-maybe used, as for example, the cups instead of being made of copper or aluminum, may be of brass or nickel. Instead of steel, alloys having similar properties may be used. These and other changes in the detail of my in- 5 vention may be within the scope thereof, and the invention to be broadly construed and not to be limited cept y the claims appended hereto.

I claim:

1. An electrode structure comprising a metal electrode of high conductivity, a body of a molded insulating composition 01' glass-bonded powdered mica, a double flanged sleeve of higher coemcient oi. than said composition. said electrode through said sleeve and being flxed thereto, said flanges extending outwardly from said sleeve, said composition filling the space between said flanges and being compressed by axial shrinkage of said sleeve, said sleeve being integral with said flanges.

2. An electrode structure comprising a metal electrode, a body 0! a molded insulating composition consisting oi glass-bonded powdered mica, a metal eyelet said electrode, said composition fllling the space between said eyelet and electrode, said electrode having a pair or asses-rs 6 flanges extending laterally therefrom, said composition filling the space between said flanges and being compressed by shrinkage of said flanges, said flanges having a relatively high coelflcient oi expansion.

HENRY M. RICHARDSON.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS 

